Patients with myocardial infarction admitted on weekends have been reported to less frequently undergo invasive angiography and experience poorer outcomes. We used the Nationwide Inpatient Sample database (2003 to 2011) to compare differences in all-cause inhospital mortality between patients admitted on a weekend versus weekday for an acute non–ST-segment elevation myocardial infarction (NSTEMI) and to determine if rates and timing of coronary revascularization contributed to this difference. A total of 3,625,271 NSTEMI admissions were identified, of which 909,103 (25.1%) were weekend and 2,716,168 (74.9%) were weekday admissions. Admission on a weekend versus weekday was independently associated with lower rates of coronary angiography (odds ratio [OR] 0.88; 95% confidence interval [CI] 0.89 to 0.90; p <0.001) or utilization of an early invasive strategy (EIS) (OR 0.480; 95% CI 0.47 to 0.48; p <0.001). Unadjusted inhospital mortality was significantly higher for the cohort of patients admitted on weekends (adjusted OR 1.02; 95% CI 1.01 to 1.04; p <0.001). However, this disparity was no longer significant after adjustment for differences in rates of utilization of EIS (OR 1.01; 95% CI 0.99 to 1.03; p = 0.11). In conclusion, this study demonstrates that among patients admitted with a diagnosis of an acute NSTEMI, admission on a weekend was associated with higher inhospital mortality compared with admission on a weekday and that lower rates of utilization of EIS contributed significantly to this disparity.
In previous studies, the term “weekend effect” has been used to describe the observation of inferior outcomes in patients admitted on weekends compared with those presenting on weekdays. Current guidelines for management of acute non–ST-segment elevation myocardial infarction (NSTEMI) favor an early invasive strategy (EIS) where timely coronary revascularization is preferred over medical therapy for appropriate patients. Previously, patients with myocardial infarction admitted on weekends have been reported to undergo invasive cardiac procedures less frequently. Our study aimed to compare differences in outcomes among NSTEMI admissions on the basis of day of admission, weekend versus weekday, and to determine whether such differences resulted from disparities in use and timing of coronary revascularization.
Methods
We queried the Nationwide Inpatient Sample, a large, publicly available database of inpatient admissions in the United States from 2003 to 2011 for patients aged ≥18 years discharged with a primary diagnosis of NSTEMI ( International Classification of Diseases, Ninth Revision, Clinical Modification [ ICD-9-CM ] code, 410.71). Weekend admissions were identified using the “AWEEKEND” variable. In the Nationwide Inpatient Sample, admissions occurring between 12:00 a.m. on Saturday and 11:59 p.m. on Sunday are classified as weekend admissions, and all others are categorized as weekday admissions. EIS was defined as any coronary angiography (with or without percutaneous coronary intervention) performed on days 0 or 1 of admission. The primary outcome of interest was inhospital mortality. In addition to patient and hospital characteristics, admission on weekend was used as an independent variable in a multivariable regression model to examine predictors of inhospital mortality and of probability of performance of coronary angiography.
Results
A total of 3,625,271 discharges with a primary diagnosis of NSTEMI from 2003 to 2011 were identified, of which 909,103 (25.1%) were weekend admissions and 2,716,168 (74.9%) were weekday admissions. Patient demographics and admitting hospital characteristics are listed in Table 1 . Concurrent increases in rates of coronary angiography (53.9% in 2003% to 60.3% in 2011) and utilization of EIS (25.8% in 2003% to 40.7% in 2011) were noted over the study period for the overall population. Weekend versus weekday admission was independently associated with lower rates of coronary angiography (odds ratio [OR] 0.88; 95% confidence interval [CI] 0.89 to 0.90; p <0.001) and lower rates of EIS utilization (OR 0.480; 95% CI 0.47 to 0.48; p <0.001) using a multivariable regression analysis that adjusted for patient and hospital characteristics ( Figure 1 ). In the subgroup of patients who underwent coronary angiography during index admission, such procedures were performed later during hospitalization among patients admitted on weekends versus weekdays (mean of 1.31 vs 0.89 days; p <0.001) ( Figure 1 ).
| Admitted on: | P-value | ||
|---|---|---|---|
| Weekday (n=2,716,168) | Weekend (n=909,103) | ||
| Age, mean± SD (years) | 69.29±14.16 | 69.49±14.37 | <0.001 |
| Male | 57.2% | 56.6% | <0.001 |
| Race/ Ethnicity ∗ | |||
| White | 76.5% | 76.5% | 0.88 |
| Black | 10.2% | 10.5% | <0.001 |
| Hispanic | 7.4% | 7.5% | 0.23 |
| Primary payer | |||
| Medicare | 62.7% | 62.9% | 0.001 |
| Medicaid | 5.4% | 5.3% | 0.21 |
| Private Insurance | 24.7% | 24.5% | <0.001 |
| Geographic Region | |||
| Northeast | 22.0% | 20.6% | <0.001 |
| Midwest | 22.6% | 23.4% | <0.001 |
| South | 39.6% | 40.1% | <0.001 |
| West | 15.8% | 15.9% | 0.47 |
| Hospital Bed Size | |||
| Small | 9.4% | 9.8% | <0.001 |
| Medium | 23.7% | 24.1% | <0.001 |
| Large | 66.9% | 66.1% | <0.001 |
| Teaching Hospital | 48.0% | 45.0% | <0.001 |
| Urban Hospital | 89.4% | 88.5% | <0.001 |
| Co-morbidites † | |||
| Smoker | 27.9% | 27.6% | <0.001 |
| Dyslipidemia | 50.0% | 49.6% | <0.001 |
| Hypertension | 66.7% | 66.5% | <0.001 |
| Diabetes Mellitus | 35.7% | 35.8% | 0.50 |
| Coronary artery disease | 73.3% | 70.9% | <0.001 |
| Family History of CAD | 6.1% | 6.0% | 0.001 |
| Prior Myocardial Infarction | 10.3% | 10.8% | <0.001 |
| History of PCI | 10.2% | 10.7% | <0.001 |
| History of CABG | 8.8% | 9.4% | <0.001 |
| Congestive Heart Failure | 0.8% | 0.8% | 0.09 |
| Obesity | 10.1% | 10.2% | 0.32 |
| Renal Failure | 17.5% | 17.7% | <0.001 |
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